Interwound film material



' A. ABRAMS ET AL 2,074,313- INTERWOUND FILM MATERIAL March 16, 1937.

2 Sheets- Sheet 1 Filed March 19, 1936 March 16, 1937. A. ABRAMS El AL 2,074,313

r INTERWOUND FILM MATERIAL Filed March 19, 1936 2 Sheets Sheet 2 arm/22,4 14

Patented Mar. 16, .l937

ED; STATES) Forccy, Wausau, Wis.,

assignors to Marathon Paper Mills Company, Rothschild, Wis., a corporation of Wisconsin Application March 19, 1936, Serial No. 69,731

8 Claims. 40!. 154-2) This invention relatesto a roll of flexible sheet material interwound with fibrous sheet material. One of theobjects of this invention is to provide a .packageof flexible thermoplastic, film'material compactly wound in roll mm which may be unwound without dimculty.

, Another object of this invention is to provide a roll of flexible, pressure scalable sheet material which will retain its original form and which will 1 not expand in width or otherwise deform when subjected to higher temperatures.

A further object of this invention is to provide an interwound'pa'ckage of wax-rubber sheet material which will retain its original configuration at temperatures above normal,

.A further object of this invention is to provide a method for preventing the distortion of compactly wound rolls of thermoplastic films.

-A further object of the invention is to produce a roll of thermoplastic sheet material which can be unwound evenly without distortion of the she'et during unwinding.

Further and other objects of the invention will be apparent from the annexed drawings and the following specification.

9n the drawings: H a

Figure 1 is a perspective view of an interwound roll of film material.

Figure. 2 is a perspective view of 'a roll of film deformed by the action of heat. 1

Figure 3 isa perspective view of another roll offilm material illustrating the distorting action caused by high temperatures.

Figure 4 is a diagrammatic view illustrating an apparatus suitable for interwinding film material. Figure 5 is a' diagrammatic view of another apparatus suitable for interwinding film material. In copending applications Serial No. 693,740 I and Serial No. 40,765 we disclose a novel film ma- 4 -terial which is self-sustaining, flexible, waterproof and gasproof. Such film consists broadly of a thermoplastitc body substance and a smaller -pro-. portion-of a binder substance. Aspecific example ofsuch composition consists of a wax-rubber composition containing from at least-.fi-to 30% rubber.

. A film produced from such composition is thermoplastic, stretchable and self-sealing. We have found it convenient to supply this film-material in the formof rolls of suitable widths.

Our film has the property of shortening'in the" length of its grain direction and stretchingv or expanding in width when heated above normalroom temperature.

' I .I When our film is produced in continuous lengths =5 the grain will normally run in the direction of the length of the film strips. Consequently when rolls of the film made from a wax-rubber composition using paraffin-wax of 130 F. m. p. are produced this change of dimensions causes considerable distortion of the wound roll particularly when it is subjected to temperatures above F., thereby spoiling the original neat uniform and even contour of the roll. When higher melting point Waxes are used the temperatures at which the rollsmay be exposed without producing distortion are correspondingly higher.

The types of distortion which often occur are illustrated in Figures 2 and 3. As shown in Figure 2 a wound roll of our film becomes curved convexly and the ends 14 bulge outwardly when kept, say, at a temperature of 'F. for 24 hours.

This type o'fdistortion usually occurs when the film is wound evenly. However, when an unevenly wound roll is kept at temperatures above 90 F. pronounced end distortion of the roll may 2 occur as illustrated in Figure 3. This action appears to be caused by the contraction of the-film in the direction of its length thereby producing a radial pressure which forces the film out laterally.

' It therefore appeared that the evenness of winding and perhaps the uniformity in thickness of the greater tendency for the side where the greater pressure was exerted to expand so that the'pushing out of the film would take place almost entirely from the one side. Moreover if vgreater heat is applied on one side of a roll than on the y it could be eliminated'by interwinding a sheet of paper or other fibrous material. The function of the sheet material appears to be that of con-- It is our belief that the interwound paper produces tasting the surface of our film sufficiently to'prevent the film moving on the sheet material.-

a kind of frictional braking action, since the paper, is a relatively inelastic material which will not deform or expand and frictionally engages the film moving thereover. -When rolls of. our film are interwound with paper or other suitable suitably imprinted to give directions for use of the film and its many applications for binding and sealing purposes. We have found that generally a paper of comparatively low density or finish, in other words, a somewhat rough surthe thicker side would tend'to be of greater di-.

faced paper, is more likely to prevent expansion than one having a high finish or a smooth surface.

In general'we prefer to use a sheet of at least 17 lb. (24 x 36-480) basis weight, both from the standpoint of economy and also because a sheet of lighter weight usually does not-have sumcient strength to operate well on the winder. Where it is desirable merely to keep the film from sticking to itself but not to prevent cross expansion. we prefer to use a sheet of higher density such as super-calendered paper or glassine.

Several methods may be followed in preparing our interwound roll. According to one method, illustrated in Figure 4, our film alone is drawn through the winder until it reaches the slitter roll. The paper; Ii, for interwinding is supplied from a jumbo roll it which meets the film sheet 2 at'the slitter roll, the paper being brought on the outside of the film which in tum.is next to the slitter roll. The film 2 is supplied from roll I and is led over an automatic tension roll 3, then over spreader rolls 4, 5, 6, and over guide rolls 1 and 8 to the supporting roll I1. The paper web II is led over guidel2, then over a spreader bar It; The film and paper webs are superposed on roll I! and arethen slit simultaneously by a slitter knife i4. and from there on. carried together and wound up ,into separate rolls such as l5 and IS. The type of rewinder which we find suitable is that made by the Cameron Ma-'- chine Company and designated as No. 4 Camachine, model '7. In this winder compensation for thickness of film is made by having each small core driven independently of the others, through a friction applied on the core itself. In other words, if one side of the parent roll of our film is thicker than the other side, the roll slit from ameter. Now if these were run on the ordinary drum type of winder greater pressure would be exerted on the thick roll than on the thin roll and as a result they would be wound with different degrees of hardness.

By means of the special type of rewinder here mentioned this is compensated for and the rolls come of! inabout equal hardness of winding although one may be of greater diameter than the other.

We have found this method of interwinding paper to be suitable for all types of materials which will tend to contract in length and expand in width with increasing temperatures.

In printing our wax-rubber film and films of this type a much better printing impression can be produced when the film isbacked with paper or other suitable sheet material when fed through the press than when the film is printed without dling on the printing press and also gives a certain degree of backing to the film so that the impressions made on it by the press are clearer and better.

We may also interwind the paper with the film at the time that the film is made on the forming machine. Then in case it is not necessary to trim the roll immediately, the entire wound roll can be fed directly to the printing press for printing, after which the trimming operation is performed.

This method is illustrated in Figure 5 where the film forming composition,.such as a wax-rubber composition 25, is sheeted out on a chilled roll 21 by means of a heated doctor roll 20. The film 23 is stripped from the forming roll by a stripping roll 28 and is then led over guide roll 28 and around roll 30 where it meets the web of paper 24 which is supplied from roll 32. Web 34 passes over a spreader bar and is superposed on the wax-rubber film at roll 30. The two sheets are then wound up on the roll ll.

It is to be understood that many changes and modifications may be made in the details of our invention and it is not intended to restrict the scope of the appended claims except as necessitated by the prior art.

We claim: 1. A roll of sheet material formed from a waxrubber composition interwound with a fibrous "sheet material to prevent deformation of the roll at temperatures above F.

2. A roll of sheet material formed from a wax-- rubber composition containing from at least 6 to 30% rubber interwound with a fibrous sheet mateiial to prevent deformation of the roll at temperatures above 90 F. v

3. A roll of sheet material formed from a waxrubber composition containing from at least 6 to 30% rubber interwound with a paper of at least 17 lb. (24 x 36-480) basis weight having a slightly roughened surface. 7 4. A compactly wound roll comprising a flexible, self-sustaining, pressure sealable film interwound with a fibrous sheet material.

.- fibrous sheet material.

- 8. A method of preventing lateral distortion of a compactly wound roll of a thermoplastic film which comprises interposing a suitable material between the convolutions of said roll to retard lateral expansion of the film with increase of temperature.

. ALLEN ABRAMS.

CHARLEY L. WAGNER.

GEORGE W. FORCEY.

such backing. This permits a more even han- 

